Spring lock for X-ray apparatus



April 10, 1962 R. J. MUELLER SPRING LOCK FOR X-RAY APPARATUS 2Sheets-Sheet 1 Filed NOV. 30, 1960 FlG.l

FIG.3

INVENTOR. ROBERT J. MUELLER ATTORNEY April 10, 1962 R. J. MUELLER SPRINGLOCK FOR X-RAY APPARATUS 2 Sheets-Sheet 2 Filed Nov. 30, 1960 Aw OINVENTOR ROBERT J. MUELLER ATTORNEY United States Patent @fifice3,028,933 Patented Apr. 10, 1962 3,028,933 SPRING LOCK FOR X-RAYAPPARATUS Robert J. Mueller, Menomonee Falls, Wis., assignor to GeneralElectric Company, a corporation of New York Filed Nov. 30, 1960, Ser.No. 72,722 3 Claims. (Cl. 188-77) This invention relates to a springactuated drive shaft locking device for use in conjunction with X-rayapparatus driven by a bi-directionally rotatable shaft.

in diagnostic medical X-ray technology, the table upon or against whichthe patient rests, and the apparatus for obtaining the radiograph, mustbe locked into position during the taking of the radiograph to insurethe avoidance of mechanically introduced motion that could blur theradiographic image formed on the spot film. An advanced form of tableand related apparatus is disclosed in detail in a copending applicationentitled X-ray Apparatus by Arthur I. Kizaur, Serial No. 764,911, whichwas filed on October 2, 1958, now United States Patent No. 2,966,588,which issued on December 27, 1960. The table and apparatus in thisapplication has great flexibility by virtue of the table being capableof uninterrupted angulation through 180, and of lateral movement ofgreat length to facilitate transfer of hospital cart patients and inmany instances, eliminating the need for the transfer. The fluoroscopiccarriage and screen support has freedom of motion in three dimensions,i.e., in vertical, longitudinal and transverse directions relative tothe table. Each one of the three directions of motion for thefiuoroscopic carriage and screen support, and for the transverse motionof the table, requires a drive which for certain purposes and at certaintimes, must be stopped and locked. A drive shaft for each of thesemotions must be locked to insure the absence of chance movement andvibration when the spot film carrying cassette is shifted intoradiographic position.

To properly perform its function, the lock should be structurally simpleand positive in its action, and very strong, since the equipment to belocked in position is bulky. To insure that the X-ray exposure may bemade immediately upon the placement of the spot film in radiographicposition, the lock should operate free of mechanical backlash that mayresult in undesirable vibrations, and should be actuated as rapidly aspossible, i.e.,

the interval between the flipping of the switch and the completedcessation of movement of the drive shaft in the locked position shouldbe kept to a minimum.

It is desirable in the radiographic art that when the fluoroscopiccarriage and screen support are in position and the spot film is shiftedto its radiographic position, all of the locks for the carriage andscreen support be set automatically. Consequently, the lock utilizedshould be one adaptable and especially amenable to electrical control,and is preferably an electromagnetically actuated device.

In therapeutic medical X-ray, apparatus, such as a 300 kilovolt therapyunit, is often disposed in a manner producing very high torques,especially since non-linear motion is involved in its operation. Suchapplications require even stronger and more positive locks than does thediagnostic equipment wherein the motion of the equipment is linear.

Both diagnostic and therapeutic X-ray devices are usually installed andoperated in quiet rooms or areas. It is rotate.

highly desirable, from the viewpoint of maintaining the patientscomposure, to keep the noise level low and especially to avoid suddenloud noises. The lock used for the equipment should, therefore, be asquiet in operation as possible.

These requirements are satisfied in accordance with the principles ofthe invention; an embodiment thereof, described below, contemplates ahelical spring lock wherein two separate helical springs, having aninternal diameter smaller than that of the shaft element which they areto lock, are coaxially mounted upon and wrapped around the shaft. Eachspring is also secured to a stationary member, to thereby preventrotation of the shaft. One end of each of the springs is movable andcontrolled by a rotary solenoid, such that when the solenoid isactuated, each of the two springs is expanded or unwrapped, therebypermitting rotation of the shaft around which the springs are coaxiallywrapped.

Release of the locked shaft is achieved by mounting the springs suchthat they unwrap in opposite senses from each other; i.e., the motion ofthe spring end of one spring in a clockwise direction will expand thespring, while motion of the other in a counterclockwise direction willsimilarly expand it. This arrangement of the two springs insurespositive locking action, irrespective of in which of the two angulardirections the shaft may be tending to The solenoid drives the twospring ends, when the solenoid is actuated, in these opposite sensessimultaneously.

The helical spring lock structure is exceedingly compact because of anovel coupling mechanism between the rotary solenoid stem or shaft andthe actuating ends of the two springs.

The spring lock also has the advantage that what little backlash mayexist is of the type that the equipment is restored to its requiredposition by the spring tension itself.

The novel features which I believe to be characteristic of my inventionare set forth with particularity in the appended claims. My inventionitself, however, both as to its organization and method of operation,together with further objects and advantages thereof, may best beunderstood by reference to the following description taken in connectionwith the accompanying drawings.

In the drawings:

FIGURE 1 is a plan view, and FIGURE 2 is a longitudinal cross-sectionalview of an embodiment of a helical spring lock for X-ray apparatus, inaccordance with the principles of the invention, and is shown by way ofexample merely for purposes of illustration;

FIGURE 3 is a detail of FIGURES 1 and 2 showing the novel couplingbetween the rotary solenoid and the springs;

FIGURE 4 is a detail of FIGURES 1 and 2 showing the novel couplingbetween the actuating rings and the springs; and

FIGURE 5 is an exploded view of the device of FIG- URES 1, 2, 3 and 4.

Referring to the figures in greater detail, the elements will be setforth from left to right (relative to FIGURES l and 2). Commencing atthe left, there is a drive shaft 11 which may either be actuated by, oris responsible for actuating, the X-ray apparatus of interest. The driveshaft 11 may be actuated by a source of motive power on the left (notshown). Coaxial with and circumscrib- J ing a portion of shaft 11 is ahollow cylindrical retaining element 12 through which shaft 11 isjournaled. Immediately contiguous to, and on the right of, retainer 12is an annular cylindrical drum 13, also coaxial With and circumscribingthe shaft 11. Drum 13 is, however, rigidly secured to shaft 11 by virtueof the tapered pin passing through the drum 13 and the shaft 11 in adirection perpendicular to the longitudinal axis of the shaft, i.e.,passing through both the drum and the shaft in a diametral position.Contiguous to the right hand side of the drum 13 is a second hollowcylindrical retaining element 14, through which shaft 11 is journaled.

Circumscribing the abutting ends of retainer 12 and drum 13 is aclose-wound helical spring 15 disposed such that half of its lengthsheaths a part of retainer 12 and the other half sheaths a part of drum13. Helical spring 15 has a constant internal diameter along its entirelength which, under ordinary conditions, and when not mounted on theretainer 12, is smaller than the external diameter of that portion ofretainer 12 which is sheaths. Since the external diameter of retainer 12is the same as that of drum 13 in those regions wherein they are bothsheathed by helical spring 15, the same relationship between theinternal diameter of the spring 15 and the external diameter of the drum13 also holds as for the retainer 12.

The external diameter of the spring 15 tapers to a smaller dimensionfrom the plane defined by the abutting ends of retainer 12 and drum 13to the end of the spring in the region sheathing the drum 13.Circumscribing and coaxial with retainer 12 in the region at theleft-hand end of spring 15, is an annular adjusting ring 16 which isrigidly secured to the retainer 12 by set screws 17 and 18. Theadjusting ring 16 may be rotated to a new angular position about theretainer 12 by loosening the set screws 17-18, resetting the ring to itsnew, desired position, and then securing the screws once again. Theleft-hand tip end of spring 15 is bent upwardly in a directionperpendicular to the longitudinal axis of shaft 11, and rests in a slotin adjusting ring 16, such that the lefthand end of spring 15 is fixedlysecured to that point in the adjusting ring.

Circumscribing drum 13 in the region immediately to the right of spring15 is an annular actuating ring 19 which is free to rotate about thedrum 13 (see also the FIGURE 4 detail). The right-hand tip end 34 of thespring is in contact with and actuated by, but not secured to, a pin 33which is secured in a hole formed in the actuating ring 19. As aconsequence, rotation of actuating ring 19 in one direction(counterclockwise when viewed from the left) about drum 13 results inthe bottom end of pin 33 moving in that direction and forcing the tipend 34- of spring 15 to also move in that direction to thereby cause anexpansion of spring 15, While rotation of actuating ring 19 in theopposite direction allows the spring to grip drum 13 since pin 33 ismoved out of contact with the tip end 34 of spring 15.

Disposed coaxial to, and in a circumscribing relation about the abuttingends of drum 13 and the retainer 14, are an adjusting ring 20, a helicalspring 21 and an actuating ring 22 (from right to left), which occupythe very same relationship relative to the abutting ends of drum 13 andretainer 14 as do the adjusting rin 17, helical spring 15 and actuatingring 19 relative to the abutting ends of retainer 12 and the left-handend of drum 13. The sole difference in the relationship i the fact thehelical springs 15 and 21 are arranged to unwrap in opposite senses, sothat a rotation of the actuating rings 19 and 22 in a clockwise sense(when looking at the shaft 11 from the left) results in an expansion ofspring 21, and therefore a lessening of the radial force exerted onshaft 11 by the spring, while spring 15 remains in its contractedposition, thereby maintaining the radial force exerted on the shaft.Likewise, rotating the actuating rings 19 and 22 in a counterclockwisedirection has the opposite effect on the two springs from that which was26 is open.

4 obtained by a clockwise rotation. The terms contract" and expand withrespect to the helical springs mean nothing more than, in the case ofexpansion, a tendency for the spring to unwrap about the drum, whilecontact" indicates a tendency for the spring to wrap more tightly aboutthe drum 13.

Fixedly secured to an end of each of retainers 12 and 14, is a bracket23, which extends below the entire structure described above. Thefunction of the bracket 23 is to support a rotary magnetic solenoid 24,which may be actuated by an energy source 25 through a switch 26.Although the switch 26 i shown as a mechanical switch, it may representa relay contact actuated elsewhere by automatic electrical means.

The solenoid has a rotatable stem 27 aligned with the taper pin securingthe drum 13 to shaft 11. Mounted on the stem 27 is a cross pin 28 whichi adapted to rotate in a plane parallel to the longitudinal axis ofshaft 11 by virtue of the rotation of stem 27 when the solenoid 24 isactuated. The stem 27 is mechanically biased by a small spring at itsbase (not shown), such that cross pin 28 returns to a position parallelto the axis of shaft 11 when the solenoid 24 is not actuated, i.e., whenswitch Extending radially from each of actuating rings 19 and 22 areactuating pins 30 and 31; these pins 3031 are disposed such thatrotation of the cross pin 28 in a clockwise direction (when viewing thestem 27 from the bottom of the solenoid 24 as viewed and shown in FIGURE3) results in the right-hand side of cross pin 28 engaging pin 31 todrive the actuating ring 22 in a clockwise direction (when viewing theshaft 11 from the left), while the left-hand end of cross pin 28 willengage the pin 30 to drive the actuating ring 19 in a counterclockwisedirection (also when viewing shaft 11 from the left). The rotarysolenoid 24 has internal stops such that stem 27 cannot execute acomplete rotation, and therefore cross pin 28 cannot execute a full 360rotation.

Since springs 15 and 21 are disposed so as to unwrap in opposite sensesabout the drum 13, the actuation of rings 19 and 22 in opposite sensesresults in the two springs operating in the same way functionally, i.e.,they will both be expanded or will tend to unwrap and therefore torelease the drum 13 about which they are mounted. v nen the solenoid 24is de-energized as by the opening of switch 26, the springs 15 and 21,by their own torsional force, wind tightly about the surfaces of thedrum 13 and the retainers 12 and 14 respectively, so as to create abearing friction which locks the drum and the shaft against rotationwith respect to a fixed structure.

The locking force provided by this embodiment in accordance with theinvention, results from the tremendous friction generated through theradial force exerted by the helical springs 15 and 21 (by virtue oftheir having a smaller internal diameter than the external diameter ofdrum 13) upon the surface of drum 13. This force is readily diminishedby expanding the springs, as is done by the rotation of the actuatingrings 19 and 22, to thereby decrease the radial force exerted by thesprings. Since the force required to expand the springs 15 and 21 isonly a small fraction of the locking force provided by the embodiment,the use of a relatively small solenoid for actuation of the adjustingrings is possible.

The tapering of the springs 15 and 21 is for the purpose of eliminatingmechanical backlash in the system. As is well known in the art, thetaper speeds up the gripping action when the spring is released, bydecreasing the moment of inertia of the spring wire cross-section. Thecoupling between the actuating ring and the spring, detailed in FIGURE4, preserves this effect; if the coupling were done by bending thespring tip up into a recess in the actuating ring (which is the commonapproach and is the way the spring is coupled at its other end to theadjusting ring) then the advantage of the taper in eliminating backlashwould be lost.

Although a tapered spring has been shown, similar advantages may beobtained with two springs, each having coils of uniform thickness butdifferent from each other. The springs may be welded together in tandemso that they may, for example, replace tapered spring (or 21, or both).The spring having the thinner coils would be located in the position ofthe tapered section of spring 15, while the spring having the thickercoils would be located about the retainer 12 and the joint betweenretainer 12 and drum 13. In such an arrangement, and also when using atapered spring, it is important that the bridging coil, i.e., the coil(or coils) located about the joint or interface between retainer 12 anddrum 13, be a thick one, since the coil at that region bears theheaviest load.

The magnitude of the looking force is a function of the number of coilsin each spring, as well as the relationship of the internal diameter ofthe helix to the external diameter of the drum about which it iswrapped. Each one of these three constitutes parameters which may beutilized for varying the locking force. In this connection, it may benoted that the adjusting rings 16 and 20 may be reset so as to expand orcontact the springs 15 and 21, and thereby control the zero or initialmechanical setting of the springs as required.

The operation of the above described embodiment in accordance with theinvention may now be readily understood. In the locked condition, withswitch 26 open, the springs 15 and 21 are tightly compressed againsttheir respective retaining members 12 and 14, and the left andright-hand regions of drum 13. As a consequence, a clockwise rotation ofthe shaft 11 (looking at the shaft from the left) is opposed byfrictional forces exerted by spring 15, since a clockwise direction ofrotation inherently tends to contract spring 15 even more than itsnormal condition. A clockwise rotation of the shaft is in a directionwhich tends to expand rather than contract spring 21. Conversely, atendency of shaft 11 to rotate in a counterclockwise direction isopposed by spring 21. Actuation of the solenoid through closing theswitch 26 results in rotation of the actuating rings 19 and 22, suchthat they are rotated in opposite angular directions, thereby serving tounwrap or expand both the springs 15 and 21, and thereby removing theradial force exerted by both springs from both ends of drum 13. As longas the switch 26 remains closed, then, the solenoid remains actuated andthe cross pin 28 rotated to its stop; and therefore the springs remainexpanded and the shaft 21 free to rotate. The moment the solenoid isde-energized by opening switch 26, the cross pin 28 is rotated back toits neutral stop or position by virtue of the abovementioned biasingspring (not shown), and the springs 15 and 21 once more contract andwrap tightly about their respective portions of drum 13.

The operation of FIGURES 1-4 has been based upon the simultaneousactuation of both the springs 15 and 21 by solenoid 24 to thereby freethe shaft 11 for rotation in both angular senses. Certain X-rayapplications, however, require that a shaft be free to rotate in oneangular sense and be precluded from rotation in the opposite sense. Oneexample is a medical X-ray device wherein a sphere is mounted on a shaftand the sphere is adapted to be pressed against a portion of thepatients torso so as to gently force aside certain internal organs forthe purpose of obtaining a less obstructed radiography. This is done byrotating the rack and pinion mounted shaft along the rack in thedirection of the patient until the sphere is in place against the body(under some pressure). The shaft must be free to rotate toward thepatient, but locked against rotation in the opposite sense. After theradiograph is obtained, the shaft must be free to rotate in the senseagainst'which it was previously locked so as to remove the sphere fromits location against the patients body. Such an arrangement is readilyprovided in accordance with the principles of the invention. By removingthe cross-pin 28 and solenoid 24, each of the actuating pins 30 and 31on actuating rings 19 and 22 respectively, may be rotated separately andindependently of the other. Rotation of only one of pins 30 and 3-1permits rotation of shaft 11 in one, and only one angular sense, sincesolely one of the springs 15 or 21 is expanded.

While I have shown particular embodiments of my invention, it will beunderstood that many modifications may be made without departing fromthe spirit thereof, and I contemplate by the appended claims to coverany such modifications as fall within the true spirit and scope of myinvention.

What I claim is:

1. A spring lock for use with X-ray apparatus comprising: first andsecond cylindrical stationary members in axial alignment; a rotatablecylindrical member disposed between said first and second members and inaxial alignment therewith; a first helical spring disposed coaxiallywith and wrapped about a portion of said first stationary member andabout a portion of said rotatable member adjacent said first member; asecond helical spring dis posed coaxial with and wrapped about a portionof said stationary member and about a portion of said rotatable memberadjacent said second member; said first, second and rotatablecylindrical members all having the same external diameter; said firstand second springs having an internal diameter which when said springsare not mounted upon said first, second and rotatable members is smallerthan said external diameter of said first, second and rotatable members;and means in contactwith said springs for partially unwrapping saidsprings in the area of said rotatable member in opposite rotationalsense-s to thereby increase the internal diameters of each of saidsprings.

2. A spring look for X-ray apparatus as recited in claim 1, wherein saidmeans for unwrapping said springs includes means for unwrapping saidsprings simultaneously.

3. A spring lock for use with X-ray apparatus comprising: first, secondand third hollow members, each having a cylindrical portion, said threemembers being axially aligned in tandem relation and having equalexternal diameters; a cylindrical drive shaft coaxially dis posed tosaid three members with said drive shaft rigidly secured to and throughsaid second member which is intermediate said first and third members,said drive shaft being journaled in said first and third hollow members;a first helical spring normally having an internal diameter smaller thansaid external diameter of said first, second and third members, saidfirst helical spring being Wrapped about a portion of each of said firstand second members; a first securing means for securing one end of saidfirst spring to said first member; a first actuating annular ringcoaxial with, external to, and rotatable about said second member, saidfirst actuating ring having a pin in contact-able but unsecured relationto an end of said first spring opposite to that end secured to saidfirst securing means; a second helical spring normally having aninternal diameter smaller than said external diameter of said first,second and third members, said second helical spring being wrapped abouta portion of each of said third and second members; a second securingmeans for securing one end of said second spring to said third member; asecond actuating annular ring coaxial With, external to, and rotatableabout said second member, said second actuating ring having a pin incontactable but unsecured relation to an end of said second springopposite to that end secured to said second securing means, said firstand second actuating rings each having a radially extending pin emergingfrom its external surface in the same quadrant of said actuatingrings; arotary solenoid disposed below said second memher and having a rotatablestem extending toward said second member in a direction perpendicular tothe longitudinal axis of said drive shaft; a cross pin rigidly securedto said stem and mounted thereon in a direction perpendicular to theaxis of said stem and to said actuating pins radially extending fromsaid actuating rings and positioned on said stem to contact saidactuating pins when said stem is rotated; said first and second membersbeing mounted on a chassis and fixedly secured thereto whereby saidsecond member, said drive shaft, and said actuating rings are allrotatable relative to said first and third members.

References Cited in the file of this patent UNITED STATES PATENTSFOREIGN PATENTS Germany Oct. 6,

